Production of Electricity and Heat Storage Using Solar Mirrors

ABSTRACT

A solar energy collection array includes a plurality of individual mirrors and a plurality of receiver facets. The mirrors form a fixed multifaceted curved collection of mirrors. Each individual mirror is less than 1 square meter and is constructed of inexpensive and easily replaceable surfaces. The receiver facets are disposed as fixed curved multifaceted receivers. Each receiver facet is less than 1 square meter and is constructed of inexpensive and easily replaceable surfaces and wherein each individual mirror is aimed at one of the receiver facets so that each receiver facet is optically aligned with one of the individual mirrors thereby creating a small mirror multiple target. Different facets are utilized at different times of day and season based on the sun&#39;s position.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to solar power generators, more particularly toconcentrating solar collectors.

2. Description of the Prior Art

U.S. Pat. No. 4,137,897 teaches a reflector array that provides for thecollection and concentration of a relatively constant daily totalquantity of usable energy for one or more energy receivers through useof a collector array support configuration that provides for theefficient use of collector surface and land. This is accomplished bycombining a plurality of collectors with a support structure wherein thecollectors are carried by a terraced support surface of the structureand the reflective surfaces of the collectors lie in essentially acommon sun facing plane at noon. The terraced support surface is aterraced east-west extending wall of an enclosure such as a residential,commercial or industrial building. The system collects and concentratessolar energy for providing highly concentrated solar energy to an energyreceiver. The system includes support mechanism which includes aterraced support structure, a plurality of substantially reflectivecollector elements mounted on the support mechanism in closely spacedapart generally non-inter-element shading relationship as a unifiedarray of operative elements. The collector elements having surfacesformed as confocal parabolas for effective direction off axis withrespect to the energy receiver during most of the period for whichsunlight is available. A plurality of collector elements is positionedfor reflecting solar energy collected generally horizontally to theenergy receiver and means for driving the collector elements in trackingrelationship with the sun while continuously reflecting solar energytoward the energy receiver.

The continuing depletion of fossil and nuclear fuels may be one of themost significant long term problems facing the world. There iscondiderable disagreement regarding the size of the depletable fossiland nuclear fuel resources. Thus, increasing interest is now centeredabout renewable energy resources such as solar energy. The collectionand concentration of solar energy is an ancient art and accordingly overthe span of many centuries numerous solar energy collector andconcentrator systems have been devised. Until relatively recently thetotal solar energy collection and concentration capability of suchsystems was relatively small and generally confined to heating systemsor endothermic industrial processes requiring relatively low levels ofenergy input.

These prior art systems generally can be characterized as fixed ormovable arrays of reflectors wherein the array elements may be fixed ata given azimuth or configured to comprise heliostat elements thatinclude means for adjustment that enables automatic or manual trackingof the sun to maximize solar energy collection and concentration. Themovable arrays are generally carried by a sun tracking support that ismoved through a predetermined orbit to track around an axially disposedenergy receiver, such as a furnace, boiler, vaporizer, etc. As will bereadily appreciated, the energy collection capability, or capacity, ofsuch movable arrays is as a practical matter rather limited in view ofthe engineering problems attendant the movement of relatively largearrays. Thus, more recent attempts to collect relatively large amountsof solar energy for concentration and utilization for electrical powergeneration, industrial uses, and the like, have been centered about theutilization of a solar array collector system herein referred to as adistributed field heliostat array. As is well known, the collectorarrays presently generally used in the United States Energy Research andDevelopment Administration Solar Thermal Conversion Central PowerProjects utilize the distributed field heliostat array that distributesnumerous heliostats over a field, commonly a very large tract of land,and wherein the substantial number of heliostats are each separatelysupported on pedestals, or foundations, in the distributed field. Sincelarge expanses of collector surfaces are expensive, and since landvalues in industrialized areas are generally very high, a primary factorin reducing the capital investment directly attributable to thedevelopment of solar energy for industry is the efficient use ofcollector surface and land.

In addition, an energy receiver generally associated with a distributedfield array comprises an energy receiver means mounted on a tower andwherein the energy receiver requires an entry port for collected andconcentrated solar energy. In such an installation the entry port has arelatively wide aperture angle and to increase the energy input to thecentral receiver the spacing between the collector array and the centralreceiver must increase if the central receiver entry port aperture angleremains constant. In the distributed field collector array systems thisrequires vertical separation between the collector array and the centralenergy receiver. The system described, which has been referred to as apower tower system in a presently proposed project for 100 MWe beingdeveloped as a booster system for an existing electrical generationplant, contemplates acres of mirrors in a field to reflect the sun'sheat to a water boiler stop a 1000-foot tower. More specifically theproposed project envisions the utilization of at least 170 acres of landto accommodate the distributed field of collectors, or heliostats.Alternatively the same project proposes to attempt to utilize threetowers each 430 feet high instead of a single 1000-foot tower. Atcentral receiver towers of the aforementioned height introduce possibleair space and construction problems. Further, the energy concentrationratio for a given collector array is partially a function of shading ofone collector element by another due to sun position or angle off theaxis of the central receiver energy collector aperture and also shadingof collector elements by the tower and boiler structure. Shading in thedistributed field collector, or heliostat, array systems is a functionof both solar declination and the time of day. An open sky collectorsystem is exempified by U.S. Pat. No. 3,118,437, Jan. 21, 1964, whichalso appears to be closely related structurally to a solar energycollection system at Odeillo, France. Such systems are considered to berepresentative of the prior art systems that attempt to concentrate, aswell as collect solar energy from the previously discussed distributedfield heliostat arrays. These systems are characterized by theutilization of duplex reflector systems which it will be appreciated arenot generally suitable for concentration of solar energy at a high orderas is required for cost effective solar energy utilization for powergeneration, and the like.

U.S. Pat. No. 7,906,722 teaches a concentrating solar collector cellincludes primary and secondary mirrors disposed on opposing convex andconcave surfaces of a light-transparent optical element. Light enters anaperture surrounding the secondary mirror, and is reflected by theprimary mirror toward the secondary mirror, which re-reflects the lightonto a photovoltaic cell mounted on a central region surrounded by theconvex surface. The primary and secondary mirrors are preferably formedas mirror films that are deposited or plated directly onto the opticalelement. A concentrating solar collector array includes a sheet-likeoptical panel including multiple optical elements arranged in rows. Thephotovoltaic cells are mounted directly onto the optical panel, and theprimary mirrors of the individual collector cells include metal filmsegments that are coupled by the photovoltaic cells to facilitatetransmission of the generated electrical energy. Bypass diodes areconnected in parallel with the photovoltaic cells. The concentratingsolar collector includes a solid, light-transparent optical elementhaving a first side including a relatively large convex surface, asecond side including an aperture surface, and a relatively small curvedsurface defined in a central portion of the aperture surface, whereinthe aperture surface is substantially flat such that parallel lightbeams directed perpendicular to and passing through the aperture surfaceremain parallel while passing through the optical element between theaperture surface and the convex surface; a primary mirror disposed onthe convex surface and a secondary mirror disposed on the curvedsurface. The concentrating solar collector also includes a photovoltaicelement disposed in a central region surrounded by the convex surface.

Photovoltaic solar energy collection devices used to generate electricpower generally include flat-panel collectors and concentrating solarcollectors. Flat collectors generally include photovoltaic cell arraysand associated electronics formed on semiconductor (e.g.,monocrystalline silicon or polycrystalline silicon) substrates, and theelectrical energy output from flat collectors is a direct function ofthe area of the array, thereby requiring large, expensive semiconductorsubstrates. Concentrating solar collectors reduce the need for largesemiconductor substrates by concentrating light beams (i.e., sun rays)using, e.g., a parabolic reflectors or lenses that focus the beams,creating a more intense beam of solar energy that is directed onto asmall photovoltaic cell. Thus, concentrating solar collectors have anadvantage over flat-panel collectors in that they utilize substantiallysmaller amounts of semiconductor. Another advantage that concentratingsolar collectors have over flat-panel collectors is that they are moreefficient at generating electrical energy. A problem with conventionalconcentrating solar collectors is that they are expensive to produce,operate and maintain. The reflectors and/or lenses used in conventionalcollectors to focus the light beams are produced separately, and must bepainstakingly assembled to provide the proper alignment between thefocused beam and the photovoltaic cell. Further, over time, thereflectors and/or lenses can become misaligned due to thermal cycling orvibration, and become dirty due to exposure to the environment.Maintenance in the form of cleaning and adjusting the reflectors/lensescan be significant, particularly when the reflectors/lenses are producedwith uneven shapes that are difficult to clean. What is needed is aconcentrator-type PV cell and array that avoids the expensive assemblyand maintenance costs associated with conventional concentrator-type PVcells.

U.S. Pat. No. 4,103,151 teaches a solar powered engine and trackingsystem which includes a piston working within a cylinder for turning adrive shaft for driving an electrical generator or performing otheruseful work, a solar concentrator having a plurality of mirrors, eachreflecting Sun light on a common focal point on the end of the cylinderfor heating a flash boiler located thereon, preheated water from asource is injected into the flash boiler by a pump powered by the driveshaft timed according to piston movement after operating the piston, thesteam is then vented from the boiler by valve means operated from thedrive shaft. A starter motor is provided to initially start the engineoperating by rotating the drive shaft until the piston movement isself-sustaining. The entire device is enclosed in a solar energycollector panel for elevating the temperature of the system so as tomaintain the water at a sufficient temperature with a minimum ofexternal heating. The collector may also be utilized for separateexternal heating purposes. Sensor controlled motors track the relativemovement of the Sun and Earth and continually position the collector formaximum solar energy concentration.

U.S. Pat. No. 7,872,192 teaches a planar concentrator solar power modulewhich has a planar base, an aligned array of linear photovoltaic cellcircuits on the base and an array of linear Fresnel lenses or linearmirrors for directing focused solar radiation on the aligned array oflinear photovoltaic cell circuits. The cell circuits are mounted on aback panel which may be a metal back plate. The cell circuit area isless than a total area of the module. Each linear lens or linear mirrorhas a length greater than a length of the adjacent cell circuit. Thecell circuit may have cells mounted in shingle fashion to form ashingled-cell circuit. In an alternative module, linear extrusions onthe circuit element have faces for mounting the linear mirrors fordeflecting sun rays impinging on each mirror onto the shingled-cells.The linear extrusions are side-wall and inner extrusions with triangularcross-sections. The circuit backplate is encapsulated by lamination forweather protection. The planar module is generally rectangular withalternating rows of linear cell circuits and linear lenses or linearmirrors. The planar concentrator solar power module apparatus includes aplanar base, base formed by a planar metal back sheet and an electricalinsulating film on the metal back sheet, plural parallel linearly spacedaligned arrays of linear photovoltaic cell circuits on the base, thecell circuits further comprising plastic sheets and silicon cellssandwiched between the plastic sheets, the arrays being spaced apart onthe base more than a width of an array, a metal frame surrounding themodule and extending upward away from the planar base, a glass frontplate mounted on the metal frame and spaced from the silicon cells, andan array of linear planar Fresnel lenses on the glass front plate spacedabove the base for directing focused solar radiation on the alignedarrays of linear photovoltaic cell circuits, and wherein the metal backsheet spreads and conducts heat laterally away from the silicon cellssandwiched between the plastic sheets on the base.

Solar cells generate electricity but at a cost which is too high tocompete with electricity from the electric power company. It isgenerally acknowledged that the solar panel cost will have to drop toapproximately $1 to $2 per installed Watt before solar cells can competein this large potential market. Today's cost for solar panels is in the$6 to $7 per Watt range. Three different approaches have been pursued inattempts to resolve this cost problem.

The conventional approach is to use large silicon solar cells tiled inplanar modules where the cell area represents over 80% of the totalpanel area. The cells in this approach can be single crystal or largegrain polycrystalline cells. This approach represents over 90% of themarket but the cost of this approach has bottomed out and no furthercost reductions are expected. The second approach is based on theassumption that the cost of silicon wafers is too high and one needs tomake low cost thin film cells. The argument is that paint is cheap andthat maybe a way can be found to make paints generate electricity. Thisthin film approach includes amorphous silicon and small grain-sizepolycrystalline materials like CuInSe2 and CdTe. The problem with thisapproach has been that destroying the crystal material degrades solarcell performance. To date, this approach has not yielded modules costingless than $8 per Watt. The third approach is based on concentrating thesunlight onto small single crystal cells using larger inexpensiveplastic lenses or metal mirrors. This approach allows more efficientcells to be used and makes good technical sense. However, the problemswith this approach are not technical but instead relate to business andpolitics. Solving the business problems inherent in this approach is thefocus of this invention.

Serious attempts to develop solar concentrator photovoltaic systems canagain be divided into three parts. First, attempts have been made to usepoint focus lenses and 30% efficient cells where the systems operate athigh concentration ratios, e.g. approximately 500 suns. The problem hereis not with the technology. The various components work, and systemshave been demonstrated. The problem here is that the investment requiredto create positive cash flow is too large. Large companies will not takethe risk and small companies do not have the resources and thegovernment is not helping. The 30% cells are not being manufactured andinvestment is required here. Furthermore, trackers with the requiredaccuracy are not being manufactured. Again investment is required.Investment is also required for the thermal management and lenselements. Finally, these systems are not cost effective unless made inlarge sizes and in large volumes and there are no intermediate marketsother than the utility scale market. The second approach to solarconcentrators involves the use of arched linear Fresnel lenses andlinear silicon solar cell circuits. These systems are designed tooperate at approximately 20 suns. This is also a technically provenapproach but this approach also suffers from the investment problem.Here, investment is again required for special lenses, trackers, andthermal management systems. Here, the plan is that the cells will beavailable from the cell suppliers who make planar arrays. However, thispresents two problems. The first problem is that the planar cells haveto be significantly modified to operate at 20 suns. The second problemis that the planar cell suppliers are not motivated to cooperate. Forexample, suppose that the concentrator approach proves to be cheaper andthe market expands by three times. The problem for the planar cellsuppliers is that their part will actually shrink by 3/20 times. Again,these systems are not cost effective unless made in large sizes and inlarge volumes and there are no intermediate markets other than theutility scale market. The third approach to solar concentrator systemswas initiated by the planar module manufactures. Realizing that if theirone sun planar module were operated at 1.5 suns, they could produce 1.5times more power and consequently reduce the cost of solar electricityby 1.5 times, they built a system using edge mirrors to deflect sunlightfrom the edge areas onto their panels. Unfortunately, this approach wastechnically naive. The problem encountered was that the modules thenabsorbed 1.5 times more energy and there was no provision to remove theadditional heat. This then affected the module lifetime. Solarconcentrators require very high investments to scale up production of anew concentrator cell. The investment required for manufacturingscale-up versions of a new cell is prohibitive. Another problem thatneeds to be solved is the cell-interconnect problem. There is a need fora solar concentrator module that is a retrofit for a planar module andthat is easier and cheaper to make. The business infrastructure fortrackers and lenses should already be in-place. The heat load should beeasily manageable. Investment requirements should be manageable and itshould not threaten existing cell suppliers. Cells to be used should beavailable with very minor changes relative to planar cells. Therefore,low cost cells should be available from today's cell suppliers. Finally,it should be usable in early existing markets in order to allow earlypositive cash flow.

U.S. Pat. No. 7,388,146 teaches a planar concentrator solar power modulehas a planar base, an aligned array of linear photovoltaic cell circuitson the base and an array of linear Fresnel lenses or linear mirrors fordirecting focused solar radiation on the aligned array of linearphotovoltaic cell circuits. The cell circuits are mounted on a backpanel which may be a metal back plate. The cell circuit area is lessthan a total area of the module. Each linear lens or linear mirror has alength greater than a length of the adjacent cell circuit. The cellcircuit may have cells mounted in shingle fashion to form ashingled-cell circuit. In an alternative module, linear extrusions onthe circuit element have faces for mounting the linear mirrors fordeflecting sun rays impinging on each mirror onto the shingled-cells.The linear extrusions are side-wall and inner extrusions with triangularcross-sections. The circuit backplate is encapsulated by lamination forweather protection. The planar module is generally rectangular withalternating rows of linear cell circuits and linear lenses or linearmirrors. The method of assembling a planar concentrator solar powermodule includes the steps of obtaining existing, readily availablecommercial planar solar cells, each solar cell having a continuous gridelectrode, cutting the solar cells in segments, each resulting segmentcomprising a portion of the grid electrode, mounting the divided cellsin precisely spaced rows on a metal beat spreader back plate and forminga circuit element, connecting the cells in series to form linear circuitrows, mounting flat, linear mirrors on the plate, alternating the linearcircuit rows and the flat, linear mirrors in the circuit element,deflecting sun rays with the linear mirrors on to the linear circuitrows, concentrating solar energy into the linear circuit rows,transferring waste heat to the metal heat spreader back plate spreadingthe waste heat laterally through the metal plate so that a temperatureof the metal plate is nearly uniform, and providing optimal thermalenergy management. Solar cells generate electricity but at a cost whichis too high to compete with electricity from the electric power company.It is generally acknowledged that the solar panel cost will have to dropto approximately $1 to $2 per installed Watt before solar cells cancompete in this large potential market. Today's cost for solar panels isin the $6 to $7 per Watt range. Three different approaches have beenpursued in attempts to resolve this cost problem.

The conventional approach is to use large silicon solar cells tiled inplanar modules where the cell area represents over 80% of the totalpanel area. The cells in this approach can be single crystal or largegrain polycrystalline cells. This approach represents over 90% of themarket but the cost of this approach has bottomed out and no furthercost reductions are expected. The second approach is based on theassumption that the cost of silicon wafers is too high and one needs tomake low cost thin film cells. The argument is that paint is cheap andthat maybe a way can be found to make paints generate electricity. Thisthin film approach includes amorphous silicon and small grain-sizepolycrystalline materials like CuInSe2 and CdTe. The problem with thisapproach has been that destroying the crystal material degrades solarcell performance. To date, this approach has not yielded modules costingless than $8 per Watt. The third approach is based on concentrating thesunlight onto small single crystal cells using larger inexpensiveplastic lenses or metal mirrors. This approach allows more efficientcells to be used and makes good technical sense. However, the problemswith this approach are not technical but instead relate to business andpolitics. Solving the business problems inherent in this approach is thefocus of this invention. Serious attempts to develop solar concentratorphotovoltaic systems can again be divided into three parts. First,attempts have been made to use point focus lenses and 30% efficientcells where the systems operate at high concentration ratios, e.g.approximately 500 suns. The problem here is not with the technology. Thevarious components work, and systems have been demonstrated. The problemhere is that the investment required to create positive cash flow is toolarge. Large companies will not take the risk and small companies do nothave the resources and the government is not helping. The 30% cells arenot being manufactured and investment is required here. Furthermore,trackers with the required accuracy are not being manufactured. Againinvestment is required. Investment is also required for the thermalmanagement and lens elements. Finally, these systems are not costeffective unless made in large sizes and in large volumes and there areno intermediate markets other than the utility scale market. The secondapproach to solar concentrators involves the use of arched linearFresnel lenses and linear silicon solar cell circuits. These systems aredesigned to operate at approximately 20 suns. This is also a technicallyproven approach but this approach also suffers from the investmentproblem. Here, investment is again required for special lenses,trackers, and thermal management systems. Here, the plan is that thecells will be available from the cell suppliers who make planar arrays.However, this presents two problems. The first problem is that theplanar cells have to be significantly modified to operate at 20 suns.The second problem is that the planar cell suppliers are not motivatedto cooperate. For example, suppose that the concentrator approach provesto be cheaper and the market expands by three times. The problem for theplanar cell suppliers is that their part will actually shrink by 3/20times. Again, these systems are not cost effective unless made in largesizes and in large volumes and there are no intermediate markets otherthan the utility scale market. The third approach to solar concentratorsystems was initiated by the planar module manufactures. Realizing thatif their one sun planar module were operated at 1.5 suns, they couldproduce 1.5 times more power and consequently reduce the cost of solarelectricity by 1.5 times, they built a system using edge mirrors todeflect sunlight from the edge areas onto their panels. Unfortunately,this approach was technically naive. The problem encountered was thatthe modules then absorbed 1.5 times more energy and there was noprovision to remove the additional heat. This then affected the modulelifetime.

Solar concentrators require very high investments to scale up productionof a new concentrator cell. The investment required for manufacturingscale-up versions of a new cell is prohibitive. Another problem thatneeds to be solved is the cell-interconnect problem. There is a need fora solar concentrator module that is a retrofit for a planar module andthat is easier and cheaper to make. The business infrastructure fortrackers and lenses should already be in-place. The heat load should beeasily manageable. Investment requirements should be manageable and itshould not threaten existing cell suppliers. Cells to be used should beavailable with very minor changes relative to planar cells. Therefore,low cost cells should be available from today's cell suppliers. Finally,it should be usable in early existing markets in order to allow earlypositive cash flow. Effective solar flux at the earth's surface rangesbetween 100-200 W/m2.

Current technologies for solar collection include photovoltaic (PV)panels which directly convert light into electric energy, mirrors toredirect/concentrate solar power (CSP) onto a target heat collectorwhich drives a generator, PV panels realistically produce an averageoutput of 10-25 W/m2 (10-15% efficiency), depending mostly ongeographical area and mirror based installations typically produce 35-55W/m2 of mirrors, but a much larger area is needed for the completeinstallation so real output is about 5-10 W/m2. Efficiencies of thecurrent technologies are predicted to increase by only about 50% overthe next 15 years. The current cost for installation of a PV basedsystem is about $200/m2. A mirror based system costs about $130/m2 ofmirrors. The current cost of building a concentrated solar power stationis typically about $2.5 to $4 per watt. Therefore, a 250 MW@peak stationwould cost $600-1,000 million to build i.e. yield power at 12 to 18cents per kilowatt-hour. A 1,000 MW@peak coal or gas powered electricpower station requires about 1 square kilometer of space. A 1,000MW@peak PV or mirror based power station requires about 20-25 squarekilometers. These low efficiencies, enormous land area requirements andhigh installation costs are still the major barrier to reasonable ROIsin this industry. Government incentives and subsidies are invariablyinvolved in any small scale (home 3 KW systems—cost: $7,000 per KW) tolarge scale (50 MW and up) installations.

The inventors hereby incorporate all of the above referenced patentsinto his specification.

SUMMARY OF THE INVENTION

The present invention is generally directed to a solar energy collectionarray which includes a plurality of individual mirrors and a pluralityof receiver facets.

It is a first aspect of the present invention that the mirrors form afixed multifaceted curved collection of mirrors. Each individual mirroris less than 1 square meter and is constructed of inexpensive and easilyreplaceable surfaces.

It is a second aspect of the present invention that the receiver facetsare disposed as fixed curved multifaceted receivers. Each receiver facetis less than 1 square meter and is constructed of inexpensive and easilyreplaceable surfaces. Each individual mirror is aimed at one of thereceiver facets so that each receiver facet is optically aligned withone of the individual mirrors thereby creating a small mirror multipletarget. Different facets are utilized at different times of day andseason based on the sun's position.

Other aspects and many of the attendant advantages will be more readilyappreciated as the same becomes better understood by reference to thefollowing detailed description and considered in connection with theaccompanying drawing in which like reference symbols designate likeparts throughout the figures. The features of the present inventionwhich are believed to be novel are set forth with particularity in theappended claims.

DESCRIPTION OF THE DRAWING

FIG. 1 is schematic drawing of a small mirror multiple target (SMMT) fora solar energy collection array according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1 a small mirror multiple target (SMMT) 110 for asolar energy collection array includes a plurality of individual mirrors111 and a plurality of receiver facets 112. The mirrors 112 form a fixedmultifaceted curved collection of mirrors. The receivers facets 112 areas fixed curved multifaceted receivers. Each mirror 111 is aimed one ofthe receiver facets 112. The individual mirror and receiver facets aresmall (less than 1 square meter each) and are constructed of inexpensiveand easily replaceable surfaces. These are not focal plane focusingarrays (such as parabolic or Fresnel mirrors). Different facets areutilized at different times of day (and season) based on the sun'sposition. A larger installed mirror/collector area is required comparedto concentrating systems but this is easily offset by the loweredinstallation and maintenance costs.

The rise in fuel prices in the world and environmental concerns haveaccelerated efforts to develop viable energy production throughabsorption of the energy of sunlight. This is currently done by severalknown methods—Photovoltaic (PV) panels—directly convert light intoelectric energy and solar mirrors to redirect/concentrate solar power(CSP) onto a target heat collector which drives a generator. PVfacilities can be very large but also the size of an average house roof.CSP facilities require very large space, are typically far from citiesand require transferring electricity over long distances and expensiveroutine maintenance. Construction costs of these facilities are huge.The result is power which is typically 3 to 5 times more expensive thancommon fossil fuel or nuclear technologies. An inherent drawback insolar energy utilization is the lack of energy input during night timeand therefore, the need to store energy during the day for distributionduring the night. The current technologies utilize expensive parabolicor tubular mirrors and complex solar tracking mountings. Heat isconcentrated and delivered to a target which heats up the boilers usedto drive the generators. We propose fixed multifaceted curved collectionmirrors aimed at fixed curved multifaceted receivers. The individualmirror and receiver facets are small (less than 1 square meter each) andare constructed of inexpensive and easily replaceable reflective foil(aluminized plastic) surfaces. These are not focal plane focusing arrays(such as parabolic or Fresnel mirrors). Instead, different facets areutilized at different times of day (and season) based on the sun'sposition. A larger installed mirror/collector area is indeed requiredcompared to concentrating systems but this is easily offset by thelowered installation and maintenance costs. One of the major maintenanceproblems of solar mirrors is dust and grime which collect on the mirrorsurfaces. The proposed foil surfaced mirrors will be constructed of longstrips of foil which are rolled on the two sides or the surface and arecontinuously scrolled from one side to the other side. A simple fixedbrush cleans the foil passing under it. Excess heat generated by theSmall Mirror Multiple Target (SMMT) Solar Energy Collection Array willbe stored by conduction via fluid filled metal pipes (heat exchanger)into an insulated underground sand/gravel heat accumulator. The sandwill heat up to hundreds of degrees celcius during the day. At night,the fluid filled pipes will be used to collect the accumulated heatenergy and deliver it to the boilers running the generators. Unlikeexisting mirror array facilities, SMMT is also suitable for smallcourtyards or roofs of domestic buildings and factories. Small localfacilities save power and transportation costs as opposed to the giantfacilities located away from the city that require expensive deliveryinfrastructure.

A fixed multifaceted curved collection of mirrors each of which is aimedat fixed curved multifaceted receivers. The individual mirror andreceiver facets are small (less than 1 square meter each) and areconstructed of inexpensive and easily replaceable surfaces. These arenot focal plane focusing arrays (such as parabolic or Fresnel mirrors).Different facets are utilized at different times of day (and season)based on the sun's position. A larger installed mirror/collector area isrequired compared to concentrating systems but this is easily offset bythe lowered installation and maintenance costs. Neither an aimingtechnology nor an expensive fabrication is required. Power generationuses accumulated heat to drive a working fluid. Conversely, heat can beused directly for HVAC, drying operations or industrial processing. Thecost per m2 is expected to be below one third of current technologies.Roof-top installation is practical and this is the first rooftopinstallable CSP system!

From the foregoing it can be seen that a small mirror multiple targetfor solar energy collection array has been described. It should be notedthat the sketches are not drawn to scale and that distances of andbetween the figures are not to be considered significant.

Accordingly it is intended that the foregoing disclosure and showingmade in the drawing shall be considered only as an illustration of theprinciple of the present invention.

What is claimed is:
 1. A solar energy collection array comprising: a. a plurality of individual mirrors forming a fixed multifaceted curved collection of mirrors wherein each of said individual mirrors is less than 1 square meter and is constructed of inexpensive and easily replaceable surfaces; and b. a plurality of receiver facets being disposed as fixed curved multifaceted receivers wherein each of said receiver facets is less than 1 square meter and is constructed of inexpensive and easily replaceable surfaces and wherein each individual mirror is aimed at one of said receiver facets so that each receiver facet is optically aligned with one of said individual mirrors thereby creating a small mirror multiple target (SMMT) wherein different facets are utilized at different times of day and season based on the sun's position. 